The present invention relates to a control valve and more particularly to a control valve for an installation in which it is important to be able to ensure continuous operation, as is the case particularly in oil production, in refining or generally in the chemical industry.
In such an installation, when a fluid flow or pressure is to be controlled by means of a control valve, the latter is usually fitted in series with an isolation valve upstream and an isolation valve downstream, and a bypass line equipped with a manually-controlled auxiliary control valve is placed between the ends of these three valves.
Thus, when action needs to be taken for repair of the main control valve, the two isolation valves are closed and the control is carried out manually with the aid of the auxiliary control valve during the servicing period.
This results in a control valve assembly which is very heavy, very bulky and very costly.